Storage mammals

Iron homeostasis in mammalian cells is regulated by balancing iron uptake with intracellular storage and utilization. As we will see, this is largely achieved at the level of protein synthesis (translation of mRNA into protein) rather than at the level of transcription (mRNA synthesis), as was the case in microorganisms. This is certainly not unrelated to the fact that not only do microbial cells have a much shorter division time than mammalian cells, but that one consequence of this is that the half-life of microbial mRNAs is very much shorter (typically minutes rather than the hours or often days that we find with mammals). This makes it much easier to control levels of protein expression by changing the rate of specific mRNA synthesis by the use of inducers and repressors. So how do mammalian cells... 

Zinc concentrations in seminal plasma of domestic chickens (Gallus sp.) are about 100 times lower than those for humans and most other mammals, except sheep. Concentrations of zinc in fowl seminal plasma after in vitro storage of spermatozoa for 24 h at 4°C were near the threshold values toxic to spermatozoa (Blesbois and Mauger 1989), suggesting that poultry spermatozoa normally function near their lower lethal zinc threshold. 

The function of reversible iron storage in mammals is performed by ferritin (121). X-ray crystallographic studies on apoFT from horse spleen reveal a structure... 

One way is to label the pre-existing vesicles, and then follow the destiny of the label in the vesicle size distribution. The label that has been used to this aim is ferritin, which has been entrapped into vesicles. Ferritin is an iron-storage protein in plants and mammals, and consists of a hollow protein shell of c. 12 nm containing... 

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